Vitamin D supplementation to healthy children does not affect serum osteocalcin or markers of type I collagen turnover

Abstract

Aim: New serum markers have recently been introduced in the assessment of bone turnover. Such measures are osteocalcin, the C-terminal propeptide of type I procollagen (PICP), the N-terminal propeptide of type I procollagen (PINP) and the C-terminal pyridinoline cross-linked telopeptide of type I collagen (ICTP). This study aimed to determine whether supplementation with vitamin D3 to healthy children during the winter affects bone turnover in healthy children measured by serum osteocalcin, PICP, PINP or ICTP. Methods: 12 girls and 8 boys aged 6.2-13.7 (mean 9.8) y, all proven healthy by medical examination and history, were enrolled in a double-blind, randomized, placebo-controlled, cross-over study with two 4 wk treatment periods and 2 wk washout. Vitamin D3 600 IU was given in one tablet of ABCDin® daily. On the last day of the 4 wk periods blood was sampled for assessment of serum osteocalcin, PICP, PINP, ICTP, 25-OH-vitamin D, 1,25-diOH-vitamin D and parathyroid hormone (PTH). Results: During supplementation and placebo periods serum osteocalcin (mean ± SEM) was 53.9 ± 5.7 and 54.4 ± 3.8 μg l-1 (p = 0.70), PICP was 437 ± 44 and 429 ± 41 μg l-1 (p = 0.73), PINP was 579 ± 56 and 619 ± 64 μg l-1 (p = 0.33) and ICTP was 13.4 ± 0.9 and 13.6 ± 0.7 μg l-1 (p = 0.52), respectively. Mean ± SEM serum 25-OH-vitamin D was 47.0 ± 2.3 and 33.0 ± 3.0 nmol l -1 during vitamin D3 supplementation and placebo (p < 0.001, t = 8.10, 95% CI = 10.3 to 17.6 nmol l-1), 1,25-diOH-vitamin D and PTH were 87.5 ± 4.3 and 92.0 ± 5.3 pmol l-1 (p = 0.38), and 3.97 ± 0.5 and 4.21 ± 0.4 μmol l-1 (p = 0.37), respectively. Conclusion: Supplementation with 600 IU vitamin D 3 to healthy children in the winter does not affect bone turnover as measured by serum osteocalcin, PICP, PINP or ICTP. Vitamin D supplementation to healthy children may not be recommended on the ground of concern for bone turnover.